Summary
Highlights
The nucleus acts as the cell's command center, controlling growth and protein/lipid production. It contains chromatin (DNA), which holds the cell's genetic blueprint. Inside the nucleus is the nucleolus, responsible for creating ribosomal RNA to form ribosomes. The nucleus is enclosed by the nuclear envelope, which has nuclear pores allowing material like mRNA to pass through.
The endoplasmic reticulum comes in two forms: rough ER and smooth ER. Rough ER contains ribosomes and aids in protein production, while smooth ER, lacking ribosomes, produces lipids, cholesterol, and hormones, and assists in detoxification. Proteins from the rough ER are transported in vesicles to the Golgi body, which modifies and processes them (e.g., by adding lipids/carbs or folding) before exporting them out of the cell.
Mitochondria, with their own DNA, perform cellular respiration, converting energy from fats and carbohydrates into ATP. Lysosomes contain digestive enzymes to break down food and can destroy pathogens in white blood cells. The cytoplasm is the jelly-like fluid within the cell where all organelles are dissolved, containing solutes like salts, electrolytes, and carbohydrates.
The cytoskeleton maintains cell shape and provides structural support through a network of three fibers: microtubules (largest, made of tubulin, for support and transport), microfilaments (smallest, made of actin, for elongation and contraction, aiding cell movement), and intermediate filaments (in-between size, for mechanical support).
Centrioles are active during cell division, forming the mitotic spindle which pulls apart chromosomes. Cilia are short, hair-like structures, and flagella are long, whip-like structures, both made of microtubules, playing a role in cell movement.
Plant cells have unique features not found in animal cells: a large vacuole for water, nutrients, and structural support, chloroplasts (green due to chlorophyll) for photosynthesis, and a cell wall for added protection and structural integrity. Both animal and plant cells have a selectively permeable cell membrane (phospholipid bilayer) that regulates what enters and exits the cell, using protein channels for larger molecules and ions.